In my code, I declared num1: number.
constructor(){
...
this.num1 = 0;
}
This is all inside a class.
However, when I try to log the value of this.num1 or typeof this.num1 inside a function using console.log(), it returns undefined in both cases.
I am confused as to why the value of my variable is coming up as undefined. Can anyone help me understand what might be going wrong?
It has been noted by other commenters that the probable cause is that this is not behaving as expected within the function.
If you have a class structured like this:
class Foo {
public myValue: number;
constructor() { this.myValue = 0; }
barOne() { console.log(this.myValue); }
barTwo = () => { console.log(this.myValue); }
}
The barOne and barTwo methods will demonstrate different behavior when used as callbacks externally from the class.
This situation arises when utilizing a class instance method as a callback for a button, as in your scenario.
Exploring further into the workings of this in JavaScript and TypeScript (JavaScript behaves similarly to TypeScript if ECMAScript 6 is supported) can provide valuable insights, with numerous informative articles available on the topic.
However, a straightforward solution is to utilize "arrow functions," as demonstrated in the implementation of the barTwo method above.
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